My church only believes in "fasting" when it is going to do something to help your relationship with God. If it is fasting just to fast then it is pointless. And my church does not speak about fasting food, just something of importance.
But every church is different.
There are different kinds of fasts. Did your church say exactly how they're planning it? You can have a fast where you obstain from all food and only drink water. There's a partial fast where you obstain from certain foods or meals during the day. There's what's called a Daniel's fast, where you only eat vegetables and drink water.
The whole idea of fasting is to give up something important, or making a sacrifice, to be able to more fully focus on God. When fasting, we should concentrate fully on God and prayer and worship. It's a way of drawing closer to God and allowing Him to cleanse us and to better hear from God.